Rotor for a turbomachine

ABSTRACT

A rotor for a turbomachine, having at least two bladed stages, the discs of which are detachably connected to one another, in which rotor, in order to avoid notch locations in the highly stressed discs, a first disc, at least at one side face, has a first flange which is connected to or restrained with a second flange of an adjacent disc by bolts.

FIELD OF THE INVENTION

The present invention relates to a rotor for a turbomachine, having atleast two bladed stages, the discs of which are detachably connected toone another.

BACKGROUND INFORMATION

Rotors of turbomachines generally have a plurality of stages, which areprovided with blades and the discs of which are connected to one anotherin different ways, e.g. by welding or detachably by bolting. Only stageswhich are detachably connected to one another are considered in thiscase.

In a known rotor, the discs have cylindrical or conical shells whichextend essentially in the axial direction and on whose end sections ineach case flanges in the shape of a disc ring are provided, to whichadjacent discs are connected by screws, studs or the like. If anintermediate-stage seal is not integrated in the shells, it is in eachcase clamped in place between the flanges. Such a type of connection canonly be used in the case of components having a relatively lowcircumferential velocity, such as, for example, slow-speed low-pressureturbines, since the centrifugal forces which occur in the case of discsdesigned for high circumferential velocities produce excessivecircumferential stresses in the flanged connection. The bores in theflanges constitute notch locations causing local stress increases andgreatly restrict the cyclical service life of the component.

German Published Patent Application No. 196 27 386 discloses aconnecting arrangement for two turbine rotor discs which each have discconnecting arms with through-bores into which specially designedthreaded bolts for connecting the rotor discs are inserted. The factthat radial expansion of the flanged connection occurs as a result ofcentrifugal-force effect proves to be disadvantageous especially at highcircumferential velocities.

U.S. Pat. No. 5,388,963 discloses a rotor for compressors of gasturbines, in which rotor adjacent discs are detachably connected byflanges, a first flange having slots and a second flange having holesfor receiving connecting bolts, and a separate clamp with oppositetongues, which can be bent, being used in order to prevent turning ofthe connecting bolt during assembly and dismantling.

German Published Patent Application No. 2 104 172 discloses a turbinerotor and a method of producing it, in which adjacent discs are clampedtogether via inwardly directed flanges having aligned bolt bores throughwhich a bolt is passed in each case. A problem in this case is that thebolt bores in the flange constitute notch locations causing local stressincreases and restrict the cyclical service life of the rotor.

U.S. Pat. No. 5,350,278 discloses an arrangement of spaced apart rotordiscs which are detachably bolted to one another via flanges provided onspacers, an annular space along a disc pair for structural support beingdefined by the spacers. For the bolting, bores, which constitute notchlocations, are provided in the flanges.

In high-speed low-pressure turbines, additional discs extending radiallyinwards have been provided, for example, at the intermediate-stageseals.

This is intended to limit the radial expansion in such a way that thecircumferential stresses produced as a result of the centrifugal -forceeffects are kept at a low level and the requisite cyclical service lifeis achieved. However, the additional discs lead to considerable weightdisadvantages and problems during assembly.

In a further known turbine, the disc has bores through which it isconnected by bolting to adjacent discs which have cylindrical or conicalshells with flanges. The disc body limits the radial expansion of theconnecting point as a result of centrifugal-force effect. A problem,however, is that the bores in the highly loaded disc body constitutenotch locations, which limit the service life.

U.S. Pat. No. 4,844,694 discloses a connection of rotor elements of agas turbine in which the disc lying at the connecting point has a borefor inserting a bolt, the bores in the highly loaded disc bodyconstituting notch points, which limit the service life. The lastmentioned disadvantage also exists in the bolt connection disclosed byU.S. Pat. No. 5,052,891 between rotor elements of a gas turbine, inwhich bolt connection a bore for the same is provided in the disc lyingat the connecting point.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a rotor for aturbomachine of the generic type described at the beginning, in whichrotor the discs are detachably connected to one another without extremestress increases occurring due to notch locations in the disc.

The advantage of such a refinement consists in the fact that the radialexpansion of the flanged connection by the disc body is limited, but thedisc itself has no bores or notch locations which cause the local stressincreases, which are partly extremely high.

The first flange preferably extends radially inwards at an axialdistance from the side face of the first disc while forming anintermediate space.

The first flange is designed as a disc ring which has apertures alongits inner end edge or circumferential edge.

The apertures are open towards the inside, so that the centrifugal forceproduced by the bolts can be absorbed by the marginal surface of theapertures.

Furthermore, it is advantageous that the apertures are arrangedequidistantly along the circumferential edge.

To reduce the notch effect, in each case a bore, an elongated hole or afurther aperture may be provided between the apertures.

It is highly preferable for a flange section of an intermediate-stageseal to be clamped in place in each case between the first and secondflanges, the flange section of the intermediate-stage seal preferablyhaving bores which are in alignment with the apertures of the firstflange and fix the bolts in the radial direction during assembly.

Furthermore, it is expedient that the bolts, at their ends facing thefirst disc, have a transverse portion which extends at right angles totheir longitudinal axis and with which they are supported on the innerside face of the first flange. The bolts are preferably T-head bolts.

The distance of the first flange from the side face of the first disc ispreferably as small as possible, but greater than the thickness of thetransverse portion of the bolt in order to avoid a pressure point at thehighly loaded, first disc.

The flange of an adjacent disc, at its radially inner end, has asupporting portion which extends substantially in the axial directionand on which the transverse portion of the bolts is supported in orderthus to provide anti-rotation locking of the bolts.

In a preferred refinement, the first disc has a first flange at bothside faces, so that, in this way, the discs of rotors having more thantwo stages can also be detachably connected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, in longitudinal section, a view of an exemplary embodimentof the rotor according to the present invention, this view having nohatching for the sake of clarity,

FIG. 2 shows a truncated cross-sectional view along line II—II from FIG.1, and

FIG. 3 shows, in longitudinal section, a truncated view of a furtherexemplary embodiment of the rotor according to the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a longitudinal section of an exemplary embodiment of therotor according to the present invention for a turbomachine, this rotorhaving three stages. The stages are each provided with a blade 1, 2 and3 and with a first disc 4 and two adjacent discs 5,6. The first disk 4has a flange 9 and 10 respectively at each of its two side faces 7, B.The flanges 9, 10 extend at an axial distance A from their inner sidefaces 11, 12 to the side faces 7, 8. In this way, there is anintermediate space Z, which is open towards the inside in the radialdirection, between the first disc 4 and the flanges 9, 10. The distanceA is to be kept as small as possible in order to limit the radialexpansion of the flanges 9, 10 or the flanged connection by the body ofthe disc 4.

For the detachable connection of adjacent discs 5, 6, a transverseportion 13 of a (screw) bolt 14 engages in the intermediate space Z andis supported in each case on the inner side face, such as 12 forexample, of the flange 10 after the restraining/bolting.

The discs 5, 6 adjacent to the center, first disc 4 each havecylindrical shells 16 which extend substantially in the axial directionand may also be of conical design. At their ends remote from the discs5, 6, the shells 16 each have a second flange 17, which in each case isfirmly restrained with the flanges 9, 10 of the first disc 4 by (screw)bolts 14 or the like. A supporting portion 18 running essentially in theaxial direction in each case adjoins the second flanges 17 of the discs5, 6, on which supporting portion 18 the transverse portions 13 of thebolts 14 can be supported, as a result of which rotation of the bolts 14is prevented. This ensures that no pressure points occur at the highlyloaded, first discs 4 during the fitting or tightening of the (screw)bolts 14.

In each case an intermediate-stage seal 19 is clamped in place anddetachably fastened with its flange section 20 between the flanges 9, 10of the first disc 4 and the flanges 17 of the two adjacent discs 5, 6.Alternatively, the intermediate-stage seals 19 may also be arrangedintegrally on the discs 5, 6 or their shells 16.

FIG. 2 shows a cutaway and truncated crosssectional view along lineII—II from FIG. 1, in the top partial cutaway portion of which theflange 9 is shown in a plan view. The flange 9 is designed as a discring, on the inner end face or circumferential edge 21 of whichslot-like apertures 15 which are open towards the inside in the radialdirection are provided. Inserted into one aperture 15 is a (screw) bolt14, the transverse portion 13 of which is shown by a broken line. Afterfitting, this transverse portion 13 is supported on the inner side face11 of the flange 9. In addition, in order to prevent the (screw) bolt 14from rotating during the assembly,. its transverse portion 13 issupported on the supporting portion 18 of the shell 16 of the adjacentdisc 5. Provided in each case between the apertures 15 is a relief bore22, which reduces the notching factor as a result of the aperture 15.Alternatively, the bores 22 may also be designed as elongated holes,further apertures or the like.

Shown in the bottom partial cutaway portion from FIG. 2 is the flangesection 20 of the intermediate stage seal 19, this flange section 20being designed in the shape of a disc ring and having bores 23. Thebores 23 are in alignment with the apertures 15 in the flanges 9, 10 ofthe first disc 4 as are corresponding bores 24 in the second flanges 17of the discs 5, 6 adjacent to the first disc 4. As can be seen in FIG.2, the bores 23 in the flange section 20 of the intermediate-stage seal19 are open radially towards the inside, their degree of opening beingless than their diameter, in order thus to ensure radial fixing of the(screw) bolts 14 during the assembly. Alternatively, the bores 23 mayalso be designed as closed bores.

If a rotor has more than three stages, every second stage is providedwith a first disc 4 having at least one flange 9 or 10.

FIG. 3 shows a further exemplary embodiment of the rotor according tothe invention, in which the radius R at the transition between the innerside face 8 of the first disc 4 and the flange 10 or its inner side face12 is increased for strength reasons. Since the distance A between theside face 8 of the first disc 4 and the inner side face 12 of the flange10 is consequently larger, the (screw) bolt 14 has a shear ring orcollar 25, which rests on an outer side face 26 of the flange 10 andprevents an axial displacement of the (screw) bolt 14, so that thetransverse portions 13 are not pressed against the first disc 4 duringthe assembly and do not lose their anti-rotation locking.

What is claimed is:
 1. A rotor for a turbomachine, comprising: at leasttwo bladed stages including a plurality of discs that are detachablyconnected to one another, wherein: a first disc of the plurality ofdiscs includes, at least at a side face thereof, a first flange thatwith an inner side face thereof is at as small a distance as possibletherefrom, the first flange corresponds to a disc ring including aplurality of apertures arranged along an inner circumferential edgethereof, and the plurality of apertures open radially towards an inside;and a plurality of bolts by which the first disc is connected to asecond flange of an adjacent disc of the plurality of discs, wherein:each of the bolts includes a transverse portion, each transverse portionis supported on the inner side face of the first flange after a fitting,and the second flange, at the adjacent disc, includes a supportingportion extending substantially in an axial direction and on which thetransverse portions of the bolts are supported.
 2. The rotor accordingto claim 1, wherein: the first flange extends radially inwards at anaxial distance from the side face of the first disc.
 3. The rotoraccording to claim 1, wherein: the plurality of apertures are arrangedequidistantly.
 4. The rotor according to claim 1, wherein: the disc ringincludes one of a bore and an aperture between the plurality ofapertures.
 5. The rotor according to claim 1, wherein: the second flangeincludes a plurality of bores in alignment with the plurality ofapertures of the first flange.
 6. The rotor according to claim 1,further comprising: an intermediate-stage seal including a flangesection that is clamped in place between the first flange and the secondflange.
 7. The rotor according to claim 6, wherein: the flange sectionof the intermediate-stage seal includes a plurality of bores inalignment with the plurality of apertures of the first flange.
 8. Therotor according to claim 7, wherein: the plurality of bores of theflange section fixes the bolts in a radial direction.
 9. The rotoraccording to claim 1, wherein: each one of the bolts, at an end thereoffacing the first disc, includes the respective transverse portionextending at right angles to a longitudinal axis of the respective bolt.10. The rotor according to claim 1, wherein: the bolts include T-headbolts.
 11. The rotor according to claim 1, wherein: a distance of thefirst flange from the side face of the first disc is greater than athickness of the transverse portion.
 12. The rotor according to claim 1,wherein: each one of the bolts includes a collar that is supported on anouter side face of the first flange.
 13. The rotor according to claim 1,wherein: the first flange of the first disc includes two first flanges,the side face of the first disc includes two side faces, and each of thetwo first flanges is arranged at a corresponding one of the two sidefaces.